CAIRO — On Wednesday night, when Egypt’s army chief announced the forced departure of Mr Mohamed Morsi, the streets around Tahrir Square turned into an all-night carnival. But not everyone there was allowed to celebrate. Among the masses dancing, singing and honking horns, more than 80 women were subjected to mob sexual assaults, harassment or rape. In Tahrir Square since Sunday, when protests against Morsi first began, there have been at least 169 counts of sexual mob crime.

“Egypt is full of sexual harassment and people have become desensitised to it — but this is a step up,” said Ms Soraya Bahgat, a women’s rights advocate and co-founder of Tahrir Bodyguard, a group that rescues women from assault. “We’re talking about mob sexual assaults, from stripping women naked and dragging them on the floor — to rape.”

Since Sunday, campaigners say at least one woman has been raped with a sharp object.

Such crimes have been endemic at Tahrir protests since at least the 2011 revolution, but they have never been documented in such high numbers.

“It’s been underreported because a lot of people are unwilling to come forward,” said Ms Bahgat, “and because no one wanted to disturb the sanctity of Tahrir.”

In a typical attack, lines of men push their way through the packed square, surround lone women, and start ripping at their clothes until they are naked. Some women have been violated by men using their hands.

“Suddenly, I was in the middle, surrounded by hundreds of men in a circle that was getting smaller and smaller around me,” one woman has written of the experience. “At the same time, they were touching and groping me everywhere and there were so many hands under my shirt and inside my pants.”

“We call it the circle of hell,” said Ms Bahgat, who herself narrowly escaped assault this week.

Since last November, help has been at hand. Two volunteer rescue groups — Operation Anti-Sexual Harassment (OpAntish) and Tahrir Bodyguard — have squads of rescuers patrolling the square in groups of around 15. The two organisations have slightly different tactics and uniforms, but their methods are broadly the same. They seek to fight off the attackers, sometimes with clubs and flamethrowers, and re-clothe the women — and then secret them to safe-houses nearby, or even to hospital. Mobs have been known to try to break down the safe-house doors, while some of the rescuers have been assaulted themselves.

Often, random passers-by join in the attacks. But all activists in the field feel sure the assaults are usually started by groups of men who go to the square together on crowded protest days with the specific intention of violating women.